This study will determine if the vitreous concentration of fibronectin in cases with vitreal or periretinal membranes differs from that in normal autopsy human eyes. Vitreous samples taken during vitrectomy from cases of decreased vision due to periretinal or vitreal membranes will be assayed for fibronectin concentration and processed for histopathologic examination. The findings will be correlated with the types of ocular disease causing the periretinal or vitreal membranes. In uveitis or retinal vasculitis cases in which vitreous surgery is indicated, the vitreous specimens will be processed for immunologic testing.